An architecturally rational hemostat for rapid stopping of massive bleeding on anticoagulation therapy.

Hemostatic devices are critical for managing emergent severe bleeding. With the increased use of anticoagulant therapy, there is a need for next-generation hemostats. We rationalized that a hemostat with an architecture designed to increase contact with blood, and engineered from a material that activates a distinct and undrugged coagulation pathway can address the emerging need. Inspired by lung alveolar architecture, here, we describe the engineering of a next-generation single-phase chitosan hemostat with a tortuous spherical microporous design that enables rapid blood absorption and concentrated platelets and fibrin microthrombi in localized regions, a phenomenon less observed with other classical hemostats without structural optimization. The interaction between blood components and the porous hemostat was further amplified based on the charged surface of chitosan. Contrary to the dogma that chitosan does not directly affect physiological clotting mechanism, the hemostat induced coagulation via a direct activation of platelet Toll-like receptor 2. Our engineered porous hemostat effectively stopped the bleeding from murine liver wounds, swine liver and carotid artery injuries, and the human radial artery puncture site within a few minutes with significantly reduced blood loss, even under the anticoagulant treatment. The integration of engineering design principles with an understanding of the molecular mechanisms can lead to hemostats with improved functions to address emerging medical needs.

Iontosomes: Electroresponsive Liposomes for Topical Iontophoretic Delivery of Chemotherapeutics to the Buccal Mucosa.

The targeted local delivery of anticancer therapeutics offers an alternative to systemic chemotherapy for oral cancers not amenable to surgical excision. However, epithelial barrier function can pose a challenge to their passive topical delivery. The charged, deformable liposomes-"iontosomes"-described here are able to overcome the buccal mucosal barrier via a combination of the electrical potential gradient imposed by iontophoresis and their shape-deforming characteristics. Two chemotherapeutic agents with very different physicochemical properties, cisplatin (CDDP) and docetaxel (DTX), were co-encapsulated in cationic iontosomes comprising 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) and Lipoid-S75. The entrapment of CDDP was improved by formulating it in anionic reverse micelles of dipalmitoyl-sn-glycero-3-phospho-rac-glycerol sodium (DPPG) prior to loading in the iontosomes. Cryo-TEM imaging clearly demonstrated the iontosomes' electroresponsive shape-deformable properties. The in vitro transport study using porcine mucosa indicated that iontosomes did not enter the mucosa without an external driving force. However, anodal iontophoresis resulted in significant amounts of co-encapsulated CDDP and DTX being deposited in the buccal mucosa; e.g., after current application for 10 min, the deposition of CDDP and DTX was 13.54 ± 1.78 and 10.75 ± 1.75 µg/cm2 cf. 0.20 ± 0.07 and 0.19 ± 0.09 µg/cm2 for the passive controls-i.e., 67.7- and 56.6-fold increases-without any noticeable increase in their transmucosal permeation. Confocal microscopy confirmed that the iontosomes penetrated the mucosa through the intercellular spaces and that the penetration depth could be controlled by varying the duration of current application. Overall, the results suggest that the combination of topical iontophoresis with a suitable nanocarrier system can be used to deliver multiple "physicochemically incompatible" chemotherapeutics selectively to oral cancers while decreasing the extent of systemic absorption and the associated risk of side effects.

Targeted cutaneous delivery of etanercept using Er:YAG fractional laser ablation.

The aim was to investigate the feasibility of using Er:YAG fractional laser ablation to enable topical cutaneous delivery of etanercept (ETA). Preliminary investigations into the effect of fluence on micropore depth, measured by full-field optical coherence tomography, were followed by quantitative experiments to determine ETA delivery and its cutaneous biodistribution from solution and hydrogel formulations. Visualization studies were performed using confocal laser scanning microscopy and an ETA-fluorescein conjugate. Micropore depth was linearly dependent on laser fluence. However, use of a single pulse or "pulse stacking" (i.e. multiple pulses) to apply a given fluence affected pore depth; this was accommodated mathematically by including a "stacking factor". ETA delivery into porated skin from solution and 0.8% Carbopol® formulations was equivalent: increasing ETA content in the gels from 0.5 to 1 and 2% increased ETA delivery linearly (Formulations 7-9: 5.12 ± 0.95 to 7.48 ± 1.45 and 11.2 ± 2.2 µg/cm2, respectively; 10% FAA, 89.9 J/cm2, 5 ppp); occlusion further increased ETA delivery from Formulation 9 to 23.17 ± 6.62 µg/cm2. Cutaneous biodistribution studies demonstrated that ETA was delivered in therapeutically relevant amounts to the epidermis and dermis. Topical laser-assisted delivery of ETA might expand its range of clinical indications to include recalcitrant but not widespread psoriatic plaques (clinical trial underway).

Polymeric micelle nanocarriers for targeted epidermal delivery of the hedgehog pathway inhibitor vismodegib: formulation development and cutaneous biodistribution in human skin.

Background: The aim was to investigate cutaneous delivery and biodistribution of the hedgehog pathway inhibitor, vismodegib (VSD), indicated for basal cell carcinoma (BCC), from polymeric micelle formulations under infinite/finite dose conditions. Methods: VSD-loaded micelles were characterized for drug content, particle size, and shape; a micelle gel was characterized for its rheological behavior. Cutaneous deposition and biodistribution of VSD were determined using porcine and human skin in vitro with quantification by UHPLC-MS/MS. Results: The optimal micelle solution (Zav 20-30 nm) increased the aqueous solubility of VSD by >8000-fold; drug content was stable after 4 weeks at 4°C. Application of micelle solution and micelle gel (0.086% w/v) to human skin for 12 h under infinite dose conditions resulted in statistically equivalent VSD deposition (0.62 ± 0.11 and 0.67 ± 0.14 µg/cm2, respectively). Cutaneous biodistribution in human skin under infinite (micelle solution and gel) and finite (micelle gel) dose conditions showed that the VSD concentrations obtained in the basal epidermis, at depths of 120-200 µm, were ˃3800- and ˃2300-fold greater than the IC50 reported for hedgehog signaling pathway inhibition in vitro. Conclusion: Cutaneous delivery of VSD from micelle-based formulations might enable targeted, topical treatment of superficial BCC with minimal risk of systemic exposure.

Fractional Laser Ablation for the Cutaneous Delivery of Triamcinolone Acetonide from Cryomilled Polymeric Microparticles: Creating Intraepidermal Drug Depots.

The efficacy of some dermatological therapies might be improved by the use of "high dose" intraepidermal drug reservoir systems that enable sustained and targeted local drug delivery, e.g., in the treatment of keloids and hypertrophic scars. Here, a fractionally ablative erbium:YAG laser was used to enable "needle-less" cutaneous deposition of polymeric microparticles containing triamcinolone acetonide (TA). The microparticles were prepared using a freeze-fracture technique employing cryomilling that resulted in drug loading efficiencies of ∼100%. They were characterized by several different techniques, including scanning electron microscopy, powder X-ray diffraction and differential scanning calorimetry. TA was quantified by validated HPLC-UV and UHPLC-MS/MS analytical methods. In vitro release studies demonstrated the effect of polymer properties on TA release kinetics. Confocal laser scanning microscopy enabled visualization of cryomilled microparticles containing fluorescein and Nile Red in the cutaneous micropores and the subsequent release of fluorescein into the micropores and its diffusion throughout the epidermis and upper dermis. The biodistribution of TA, i.e. the amount of drug as a function of depth in skin, following microparticle application was much more uniform than with a TA suspension and delivery was selective for deposition with less transdermal permeation. These findings suggest that this approach may provide an effective, targeted and minimally invasive alternative to painful intralesional injections for the treatment of keloid scars.

Recent advances in chitosan-based nanoparticles for oral delivery of macromolecules.

Chitosan (CS), a cationic polysaccharide, is widely regarded as a safe and efficient intestinal absorption enhancer of therapeutic macromolecules, owing to its inherent mucoadhesive feature and ability to modulate the integrity of epithelial tight junctions reversibly. By using CS-based nanoparticles, many studies have attempted to protect the loaded macromolecules against acidic denaturation and enzymatic degradation, prolong their intestinal residence time, and increase their absorption by the intestinal epithelium. Derivatives of CS such as quaternized CS, thiolated CS and carboxylated CS have also been examined to further enhance its effectiveness in oral absorption of macromolecular drugs. This review article describes the synthesis of these CS derivatives and their characteristics, as well as their potential transport mechanisms of macromolecular therapeutics across the intestinal biological membrane. Recent advances in using CS and its derivatives as carriers for oral delivery of hydrophilic macromolecules and their effects on drug transport are also reviewed.

Opening of epithelial tight junctions and enhancement of paracellular permeation by chitosan: microscopic, ultrastructural, and computed-tomographic observations.

This study investigates the effects of chitosan (CS) on the opening of epithelial tight junctions (TJs) and paracellular transport at microscopic, ultrastructural, and computed-tomographic levels in Caco-2 cell monolayers and animal models. Using immunofluorescence staining, CS treatment was observed to be associated with the translocation of JAM-1 (a trans-membrane TJ protein), resulting in the disruption of TJs; the removal of CS was accompanied by the recovery of JAM-1. Ultrastructural observations by TEM reveal that CS treatment slightly opened the apical intercellular space, allowing lanthanum (an electron-dense tracer) to stain the intercellular surface immediately beneath the TJs, suggesting the opening of TJs. Following the removal of CS, the TJs were completely recovered. Similar microscopic and ultrastructural findings were obtained in animal studies. CS nanoparticles were prepared as an insulin carrier. The in vivo fluorescence-microscopic results demonstrate that insulin could be absorbed into the systemic circulation, while most CS was retained in the microvilli scaffolds. These observations were verified in a biodistribution study following the oral administration of isotope-labeled nanoparticles by single-photon emission computed tomography. Above results reveal that CS is a safe permeation enhancer and is an effective carrier for oral protein delivery.

pH-responsive nanoparticles shelled with chitosan for oral delivery of insulin: from mechanism to therapeutic applications.

Despite advances in drug-delivery technologies, successful oral administration of protein drugs remains an elusive challenge. When protein drugs are administered orally, they can rapidly denature or degrade before they reach their targets. Such drugs also may not absorb adequately within the small intestine. As a protein drug for treating diabetes, insulin is conventionally administered via subcutaneous (SC) injection, yet often fails to achieve the glucose homeostasis observed in nondiabetic subjects. Some of this difference may relate to insulin transport: normally, endogenously secreted insulin moves to the liver via portal circulation. When administered subcutaneously, insulin moves through the body via peripheral circulation, which can produce a peripheral hyperinsulinemia. In addition, because SC treatment requires multiple daily injections of insulin, patients often do not fully comply with treatment. Oral administration of exogenous insulin would deliver the drug directly into the liver through portal circulation, mimicking the physiological fate of endogenously secreted insulin. This characteristic may offer the needed hepatic activation, while avoiding hyperinsulinemia and its associated long-term complications. This Account demonstrates the feasibility of using chitosan nanoparticles for oral insulin delivery. Nanoparticle (NP) delivery systems may provide an alternative means of orally administering protein drugs. In addition to protecting the drugs against a harmful gastric environment, the encapsulation of protein drugs in particulate carriers can avert enzymatic degradation, while controlling the drug release and enhancing their absorption in the small intestine. Our recent study described a pH-responsive NP system composed of chitosan (CS) and poly(γ-glutamic acid) for oral delivery of insulin. As a nontoxic, soft-tissue compatible, cationic polysaccharide, CS also adheres to the mucosal surface and transiently opens the tight junctions (TJs) between contiguous epithelial cells. Therefore, drugs made with CS NPs would have delivery advantages over traditional tablet or powder formulations. This Account focuses on the premise that these CS NPs can adhere to and infiltrate the mucus layer in the small intestine. Subsequently, the infiltrated CS NPs transiently open the TJs between epithelial cells. Because they are pH-sensitive, the nanoparticles become less stable and disintegrate, releasing the loaded insulin. The insulin then permeates through the opened paracellular pathway and moves into the systemic circulation.

Protease inhibition and absorption enhancement by functional nanoparticles for effective oral insulin delivery.

Complexing agents such as diethylene triamine pentaacetic acid (DTPA) are known to disrupt intestinal tight junctions and inhibit intestinal proteases by chelating divalent metal ions. This study attempts to incorporate these benefits of DTPA in functional nanoparticles (NPs) for oral insulin delivery. To maintain the complexing agent concentrated on the intestinal mucosal surface, where the paracellular permeation enhancement and enzyme inhibition are required, DTPA was covalently conjugated on poly(γ-glutamic acid) (γPGA). The functional NPs were prepared by mixing cationic chitosan (CS) with anionic γPGA-DTPA conjugate. The γPGA-DTPA conjugate inhibited the intestinal proteases substantially, and produced a transient and reversible enhancement of paracellular permeability. The prepared NPs were pH-responsive; with an increasing pH, CS/γPGA-DTPA NPs swelled gradually and disintegrated at a pH value above 7.0. Additionally, the biodistribution of insulin orally delivered by CS/γPGA-DTPA NPs in rats was examined by confocal microscopy and scintigraphy. Experimental results indicate that CS/γPGA-DTPA NPs can promote the insulin absorption throughout the entire small intestine; the absorbed insulin was clearly identified in the kidney and bladder. In addition to producing a prolonged reduction in blood glucose levels, the oral intake of the enteric-coated capsule containing CS/γPGA-DTPA NPs showed a maximum insulin concentration at 4 h after treatment. The relative oral bioavailability of insulin was approximately 20%. Results of this study demonstrate the potential role for the proposed formulation in delivering therapeutic proteins by oral route.

A review of the prospects for polymeric nanoparticle platforms in oral insulin delivery.

Success in the oral delivery of therapeutic insulin can significantly improve the quality of life of diabetic patients who must routinely receive injections of this drug. However, oral absorption of insulin is limited by various physiological barriers and remains a major scientific challenge. Various technological solutions have been developed to increase the oral bioavailability of insulin. Having received considerable attention, nano-sized polymeric particles are highly promising for oral insulin delivery. This review article describes the gastrointestinal barriers to oral insulin delivery, including chemical, enzymatic and absorption barriers. The potential transport mechanisms of insulin delivered by nanoparticles across the intestinal epithelium are also discussed. Finally, recent advances in using polymeric nanoparticles for oral insulin delivery and their effects on insulin transport are reviewed, along with their future.

Effects of chitosan-nanoparticle-mediated tight junction opening on the oral absorption of endotoxins.

Recently, we reported a pH-responsive nanoparticle (NP) system shelled with chitosan (CS), which could effectively increase the oral absorption of insulin and produce a hypoglycemic effect, presumably due to the CS-mediated tight junction (TJ) opening. It has been often questioned whether CS can also enhance the absorption of endotoxins present in the small intestine. To address this concern, we studied the effect of CS NPs on the absorption of lipopolysaccharide (LPS), the most commonly found toxin in the gastrointestinal tract. To follow their biodistribution by the single-photon emission computed tomography/computed tomography, LPS and insulin were labeled with (99m)Tc-pertechnetate ((99m)Tc-LPS) and (123)iodine ((123)I-insulin), respectively. The (99m)Tc-LPS was ingested 1 h prior to the administration of the (123)I-insulin-loaded NPs to mimic the physiological conditions. The confocal and TEM micrographs show that the orally administered CS NPs were able to adhere and infiltrate through the mucus layer, approach the epithelial cells and mediate to open their TJs. The radioactivity associated with LPS was mainly restricted to the gastrointestinal tract, whereas (123)I-insulin started to appear in the urinary bladder at 3 h post administration. This observation indicates that the insulin-loaded in CS NPs can traverse across the intestinal epithelium and enter the systemic circulation, whereas LPS was unable to do so, probably because of the charge repulsion between the anionic LPS in the form of micelles and the negatively charged mucus layer. Our in vivo toxicity study further confirms that the enhancement of paracellular permeation by CS NPs did not promote the absorption of LPS. These results suggest that CS NPs can be used as a safe carrier for oral delivery of protein drugs.

The glucose-lowering potential of exendin-4 orally delivered via a pH-sensitive nanoparticle vehicle and effects on subsequent insulin secretion in vivo.

Exendin-4 is a potent insulinotropic agent in diabetes patients; however, its therapeutic utility is limited due to the frequent injections required. In this study, an orally available exendin-4 formulation, using an enteric-coated capsule containing pH-responsive NPs, was developed. Following oral administration of (123)I-labeled-exendin-4 loaded NPs in rats, the biodistribution of the administered drug was investigated using a dual isotope dynamic SPECT/CT scanner. The results showed that the radioactivity of (123)I-exendin-4 propagated from the esophagus, stomach, and small intestine and then was absorbed into the systemic circulation; with time progressing, (123)I-exendin-4 was metabolized and excreted into the urinary bladder. In the in vivo dissolution study, it was found that the enteric-coated capsule remained intact while in the stomach; the capsule was completely dissolved in the proximal segment of the small intestine and the loaded contents were then released. Oral administration of the capsule containing exendin-4 loaded NPs showed a maximum plasma concentration at 5 h after treatment; the bioavailability, relative to its subcutaneous counterpart, was found to be 14.0 ± 1.8%. The absorbed exendin-4 could then stimulate the insulin secretion and provide a prolonged glucose-lowering effect. The aforementioned results suggest that the orally available exendin-4 formulation developed warrants further exploration as a potential therapy for diabetic patients.

Biodistribution, pharmacodynamics and pharmacokinetics of insulin analogues in a rat model: Oral delivery using pH-responsive nanoparticles vs. subcutaneous injection.

In this study, we report the biodistribution of aspart-insulin, a rapid-acting insulin analogue, following oral or subcutaneous (SC) administration to rats using the single-photon emission computed tomography (SPECT)/computed tomography (CT). Oral delivery of aspart-insulin was achieved using a pH-responsive nanoparticle (NP) system composed of chitosan (CS) and poly(gamma-glutamic acid). The results obtained in the SPECT/CT study indicate that the orally administered aspart-insulin was absorbed into the systemic circulation, while the drug carrier (CS) was mainly retained in the gastrointestinal tract.Via the SC route, the peak aspart-insulin concentration in the peripheral tissue/plasma was observed at 20 min after injection. Within 3 h, half of the initial dose (ID) of aspart-insulin was degraded and excreted into the urinary bladder. In contrast, via oral delivery, there was constantly circulating aspart-insulin in the peripheral tissue/plasma during the course of the study, while 20% of the ID of aspart-insulin was metabolized and excreted into the urinary bladder. In the pharmacodynamic (PD) and pharmacokinetic (PK) evaluation in a diabetic rat model, the orally administered aspart-insulin loaded NPs produced a slower hypoglycemic response for a prolonged period of time, whereas the SC injection of aspart-insulin produced a more pronounced hypoglycemic effect for a relatively shorter duration. Finally, comparison of the PD/PK profiles of the orally administered aspart-insulin with those of the SC injection of NPH-insulin, an intermediate-acting insulin preparation, suggests the suitability of our NP system to be used as a non-invasive alternative for the basal insulin therapy.

Enteric-coated capsules filled with freeze-dried chitosan/poly(gamma-glutamic acid) nanoparticles for oral insulin delivery.

A pH-sensitive nanoparticle (NP) system composed of chitosan and poly(gamma-glutamic acid) was prepared for the oral delivery of insulin. The biodistribution study in a rat model showed that some of the orally administered NPs were retained in the stomach for a long duration, which might lead to the disintegration of NPs and degradation of insulin. To overcome these problems, we freeze-dried NPs and filled them in an enteric-coated capsule. The small angle X-ray scattering (SAXS) profiles indicated that the freeze-drying process did not significantly disrupt the internal structure of NPs; additionally, their pH-sensitivity was preserved and the insulin release was pH-dependent. The results obtained in the native PAGE analysis indicated that the released insulin molecules were neither fragmented nor aggregated. Upon oral administration, the enteric-coated capsule remained intact in the acidic environment of the stomach, but dissolved rapidly in the proximal segment of the small intestine. Consequently, all the NPs loaded in the capsule were brought into the small intestine, thus enhancing the intestinal absorption of insulin and providing a prolonged reduction in blood glucose levels. The relative bioavailability of insulin was found to be approximately 20%. These results suggest that the formulation developed in the study might be employed as a potential approach for the oral delivery of insulin.

The characteristics, biodistribution and bioavailability of a chitosan-based nanoparticulate system for the oral delivery of heparin.

Heparin is a potent anticoagulant; however, it is poorly absorbed in the gastrointestinal tract. In this study, we developed a nanoparticle (NP) system shelled with chitosan (CS) for oral delivery of heparin; the NPs were prepared by a simple ionic gelation method without chemically modifying heparin. The drug loading efficiency of NPs was nearly 100% because a significantly excess amount of CS was used for the CS/heparin complex preparation. The internal structure of the prepared NPs was examined by small angle X-ray scattering (SAXS). The obtained SAXS profiles suggest that the NPs are associated with a two-phase system and consist of the CS/heparin complex microdomains surrounded by the CS matrix. The stability of NPs in response to pH had a significant effect on their release of heparin. No significant anticoagulant activity was detected after oral administration of the free form heparin solution in a rat model, while administration of NPs orally was effective in the delivery of heparin into the blood stream; the absolute bioavailability was found to be 20.5%. The biodistribution of the drug carrier, (99m)Tc-labeled CS, in rats was studied by the single-photon emission computed tomography after oral administration of the radio-labeled NPs. No significant radioactivity was found in the internal organs, indicating a minimal absorption of CS into the systemic circulation. These results suggest that the NPs developed in the study can be employed as a potential carrier for oral delivery of heparin.

In vivo evaluation of safety and efficacy of self-assembled nanoparticles for oral insulin delivery.

A variety of approaches have been studied in the past to overcome the problems encountered with the oral delivery of insulin, but with little success. In this study, self-assembled nanoparticles (NPs) with a pH-sensitive characteristic were prepared by mixing the anionic poly-gamma-glutamic acid solution with the cationic chitosan solution in the presence of MgSO(4) and sodium tripolyphosphate. The in vitro results found that the transport of insulin across Caco-2 cell monolayers by NPs appeared to be pH-dependent; with increasing pH, the amount of insulin transported decreased significantly. An in vivo toxicity study was performed to establish the safety of the prepared NPs after oral administration. Additionally, the impact of orally administered NPs on the pharmacodynamics (PD) and pharmacokinetics (PK) of insulin was evaluated in a diabetic rat model. The in vivo results indicated that the prepared NPs could effectively adhere on the mucosal surface and their constituted components were able to infiltrate into the mucosal cell membrane. The toxicity study indicated that the NPs were well tolerated even at a dose 18 times higher than that used in the PD/PK study. Oral administration of insulin-loaded NPs demonstrated a significant hypoglycemic action for at least 10h in diabetic rats and the corresponding relative bioavailability of insulin was found to be 15.1+/-0.9%. These findings suggest that the NPs prepared in the study are a promising vehicle for oral delivery of insulin.

Multi-ion-crosslinked nanoparticles with pH-responsive characteristics for oral delivery of protein drugs.

pH-Responsive nanoparticles composed of chitosan (CS) and poly-gamma-glutamic acid (gamma-PGA) blended with tripolyphosphate (TPP) and MgSO(4) (multi-ion-crosslinked NPs) were prepared and characterized to determine their effectiveness in the oral delivery of insulin. Their counterparts without TPP and MgSO(4) (NPs) were used as a control. FT-IR and XRD results indicated that the spontaneous interaction between CS, insulin, gamma-PGA, MgSO(4) and TPP can form an ionically crosslinked network-structure, leading to the formation of nanoparticles. Multi-ion-crosslinked NPs were more compact than NPs, while their zeta potential values were comparable. During storage, multi-ion-crosslinked NPs suspended in deionized water were stable for at least 10 weeks. Multi-ion-crosslinked NPs had a superior stability over a broader pH range than NPs. In the in vitro release study, NPs failed to provide an adequate retention of loaded insulin in dissolution media compared to multi-ion-crosslinked NPs. Transepithelial-electrical-resistance and transport experiments demonstrated that multi-ion-crosslinked NPs significantly more effectively transported insulin than NPs; confocal visualization further validated the enhanced permeation of insulin via the paracellular pathway. The aforementioned results suggest that multi-ion-crosslinked NPs are a promising carrier for improved transmucosal delivery of insulin in the small intestine.

Oral delivery of peptide drugs using nanoparticles self-assembled by poly(gamma-glutamic acid) and a chitosan derivative functionalized by trimethylation.

In the study, chitosan (CS) was conjugated with trimethyl groups for the synthesis of N-trimethyl chitosan (TMC) polymers with different degrees of quaternization. Nanoparticles (NPs) self-assembled by the synthesized TMC and poly(gamma-glutamic acid) (gamma-PGA, TMC/gamma-PGA NPs) were prepared for oral delivery of insulin. The loading efficiency and loading content of insulin in TMC/gamma-PGA NPs were 73.8 +/- 2.9% and 23.5 +/- 2.1%, respectively. TMC/gamma-PGA NPs had superior stability in a broader pH range to CS/gamma-PGA NPs; the in vitro release profiles of insulin from both test NPs were significantly affected by their stability at distinct pH environments. At pH 7.0, CS/gamma-PGA NPs became disintegrated, resulting in a rapid release of insulin, which failed to provide an adequate retention of loaded insulin, while the cumulative amount of insulin released from TMC/gamma-PGA NPs was significantly reduced. At pH 7.4, TMC/gamma-PGA NPs were significantly swelled and a sustained release profile of insulin was observed. Confocal microscopy confirmed that TMC40/gamma-PGA NPs opened the tight junctions of Caco-2 cells to allow the transport of insulin along the paracellular pathway. Transepithelial-electrical-resistance measurements and transport studies implied that CS/gamma-PGA NPs can be effective as an insulin carrier only in a limited area of the intestinal lumen where the pH values are close to the p K a of CS. In contrast, TMC40/gamma-PGA NPs may be a suitable carrier for transmucosal delivery of insulin within the entire intestinal tract.